Sharma A, Kaur G, Ravikanth M. Synthesis of unsymmetrical 2,3,7,8-tetrabromo
meso-5,10,11,16-tetraaryl- triphyrin(2.1.1) and its use in the synthesis of sterically crowded 2,3,5,7,8,10,11,16-octaarylated triphyrin(2.1.1)s.
Org Biomol Chem 2024;
22:838-849. [PMID:
38175260 DOI:
10.1039/d3ob01886e]
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Abstract
Triphyrin(2.1.1) is a 14π aromatic contracted congener of an 18π aromatic porphyrin(1.1.1.1). An unsymmetrical 2,3,7,8-tetrabromo meso-tetraaryl triphyrin(2.1.1) containing four bromides at the β-pyrrole carbons of two out of three pyrrole rings of the triphyrin core was synthesized for the first time in 90% yield by treating meso-tetraaryl triphyrin(2.1.1) with five equivalents of N-bromosuccinimide in 1,2-dichloroethane (DCE) under reflux for 8 h. The X-ray structure revealed that the triphyrin(2.1.1) macrocycle was significantly distorted in 2,3,7,8-tetrabromo meso-tetraaryl triphyrin compared to planar meso-tetraaryl triphyrin. A series of novel sterically crowded 2,3,5,7,8,10,11,16-octaaryl triphyrin(2.1.1)s were synthesized by coupling 2,3,7,8-tetrabromo meso-tetraaryl triphyrin with six different aryl boronic acids under Suzuki-Miyaura coupling conditions. NMR, absorption, electrochemical and theoretical studies revealed that the structure and electronic properties were drastically altered in the 2,3,5,7,8,10,11,16-octaaryl triphyrin(2.1.1) series due to the presence of four additional aryl groups at the β-pyrrole carbons which caused steric crowding at the periphery of the triphyrin core resulting in a decrease in effective π-conjugation in the triphyrin(2.1.1)s.
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